Not Applicable
Not Applicable
This invention relates to security systems, and more particularly to a fire-rated dome housing assembly for mounting a pivotable video security camera.
Dome housings for mounting video cameras employed in security systems typically include a metal housing portion and a plastic dome portion in which the housing portion is mountable through a hole in a ceiling and the dome portion is attached to the housing portion. In many installations, the ceiling is a dropped or false ceiling that is spaced apart from a structural ceiling by joists or other supporting members. The enclosed volumetric space between the structural ceiling, dropped ceiling, and adjacent supporting members often functions as an air plenum for a heating and air conditioning system.
However, there are disadvantages to currently available dome housings. The volumetric space or plenum height between the structural ceiling and the false ceiling can be as little as 8.9 cm (3.5 inch), which is less than the height of many metal housing portions. The dome housings typically mount by snap clips to the hole in the ceiling material, which is typically sheet rock or insulation panel material. At high temperatures, the combined mass of the dome housing and its enclosed device can cause a collapse of the false ceiling, thereby compromising the plenum air flow and the ceiling fire-rating.
Prior workers have addressed the ceiling collapse problem by providing metal straps for securing the housing to the joists or to the structural ceiling. For example, the model MP121/141 Recessed Housing manufactured by Videolarm of Decatur, Ga. meets fire codes and includes metal straps for securing the housing to joists. However, the MP121/141 housing is 17.9 cm (7.05 inches) high, which is too tall to fit in many air plenums.
What is needed, therefore, is a dome housing capable of being mounted in an 8.9 cm (3.5 inch) or higher volumetric space or plenum, forestalling ceiling collapse during a fire, and maintaining a ceiling fire rating.
An object of this invention is, therefore, to provide a dome housing apparatus that can be mounted in an 8.9 cm (3.5 inch) or higher volumetric space or plenum.
Another object of this invention is to provide a dome housing apparatus that during a fire forestalls ceiling collapse.
A further object of this invention is to provide a dome housing apparatus that during a fire maintains the ceiling fire rating.
A preferred embodiment of a fire-rated dome housing assembly of this invention is mountable in a volumetric space formed between a structural ceiling and a false ceiling that is spaced apart from the structural ceiling by joists or supporting members. The false ceiling may be spaced apart from the structural ceiling by as little as about 8.9 cm (3.5 inch).
The housing assembly includes a housing that is mountable through a hole in the false ceiling, and is protected from heat by a thermal insulation blanket that encloses the portion of the housing that extends into the plenum. Support straps are attached to a ceiling ring that surrounds the hole for securing the housing assembly to the supporting members. The support straps pass between the ceiling ring and the false ceiling, and extend upward for attachment to the supporting members. The housing includes a lower portion that protrudes below the false ceiling and includes a mounting flange at its lower margin. Because the lower portion protrudes below the false ceiling, a spacing collar is fastened to the ceiling ring by threaded spacers that extend the protrusion distance below the false ceiling. The spacing collar is decorative and protects the housing from flame and heat.
A hemispherical LEXAN plastic dome-shaped cover piece (hereafter xe2x80x9cdomexe2x80x9d) is suspended by a trim ring that is secured to the mounting flange with tamper-resistant screws. The housing preferably encloses at least one electronic device, such as a video camera.
The housing assembly of this invention is advantageous because it meets the standard small-scale horizontal fire endurance test referred to as ASTM E119, mounts in a restricted height volumetric space or plenum, prevents false ceiling collapse in the event of a fire, and maintains a one-hour ceiling fire rating.
Additional objects and advantages of this invention will be apparent from the following detailed description of a preferred embodiment thereof that proceeds with reference to the accompanying drawings.